Who和whom都是询问人物的疑问词，基本上who是问主语(subject)而whom是问宾语(object)。 Examples: Q: Who has eaten the apple? A: Tom has eaten the apple. (要求的答案Tom是subject，所以用who问。) Q: Whom are you talking to? A: I'm talking to Peter. (要求的答案Peter的object，所以用whom问。) 不过在现代英语中，用who比whom更普遍，即"Whom are you talking to?"多变成"Who are you talking to?"。 不过，在子句(clauses)中，whom却不能被who取代。 Examples: 1. I will only tell the secret to that person. I can trust that person. --> I will only tell the secret to whom I can trust. 2. I have fallen in love with her. I met her in Bangkok last week. --> I have fallen with love with whom I met in Bangkok last week. 以上两句，that person和her都是object，所以变成clause的时候用whom来指示。这些时候whom不能用who所取代。
参考: .knowledge.yahoo/question/?qid=7007020401261
quite well-explained. but unfortunately
it's copied from others. rite?
who [hu:] pron. 谁
那...的(人) WHO abbr. 世界卫生组织 who [hu:] pron. (宾格whom; 所有格whose) [疑问代词]谁; 哪位 [连接代词]谁 [限制性的关系代词]...的人 [非限制性的关系代词]他[她]; 他[她]们 [古][省略先行词的关系代词]...的人 W-is that? 那是谁? He is a man who is of value to the people. 他是一个有益于人民的人。 Whom did you see? 你看见谁了? That's the man who came to our house yesterday. 那就是昨天到过我们家来的人。 My cousin
who is a painter
is in Japan at present. 我的表哥是画家
他现在在日本。 Who breaks pays. 损坏者要赔。 who n. 有关人物 the who and the why of it 与该事有关的人物及其发生的原因 who iswho(=who's who) 知道某一范围内所有的人是谁(It took the new teacher a few days to remember who was who in the class. 这位新教师花了几天时间记住班上学生的名字) 名[要]人
有影响人士 Who's Who 名人录
名人词典 WHO =White House Office 白宫办公厅[美]; World Health Organization 世界卫生组织 whom [hu:m
hum] pron. 谁 whom [hu:m
hum] pron. (who 的宾格
但在口语中常用who 代替) [疑问代词]谁 [关系代词]...的人;...那些人; 他(她)们 [古][省略先行词的关系代词]...的人 Whom [Who]did you meet in the street yesterday? 昨天你在街上遇见了谁? I don't know to whom I ought to address the request. 我不知道该向谁提出此项请求。 That is the man whom I met in Beijing last year. 他就是我去年在北京碰见的那个人。 My brother
whom you met the other day
has gone abroad. 前几天你遇见过的我的那个兄弟
出国去了。 whom(=those whom) the gods love die young. [谚]神爱者去世早
聪明者不长寿。
参考: me
whom is object who is wh－question